The modern tendency in the food industry has been to use extracts wherever possible instead of the natural products. This has been especially true with natural spices such as vanilla, cinnamon, cloves, black pepper and the like.
The use of extracts has a number of decided advantages. For example it is easier to provide and maintain the extracts in a germ free condition than is the case with the natural products. Additionally the vegetable "ballast" is avoided if spice extracts or concentrates are used since the actual spicy components of the natural spices are present in only very minor amounts.
A number of methods have been devised to extract the flavor and aroma constituents from the natural products. The extraction solvents usually employed are organic solvents since the desired constituents are not usually water soluble. This has caused considerable difficulty since it is quite difficult to remove the last traces of the solvent from the residue.
Moreover, there is the possibility of chemical reaction between the solvent and spice with the danger of the production of toxic substances.